regardless of

[JEic]

This sentence from https://dictionary.cambridge.org/dictionary/english/regardless:

The plan for a new office building went ahead regardless of local opposition.

I thought there should be a "comma": The plan for a new office building went ahead, regardless of local opposition.

When do I need to put a comma and when there is no need?

 

[teechar]

This sentence is from https://dictionary.cambridge.org/dictionary/english/regardless:

When do I need to put a comma, and when is there is no need for one?

Note the corrections above.
To answer your question, a comma is not necessary in that sentence, but it would not be wrong either.

You might find the explanation in the following links helpful.

Comma Before or After "Regardless": Rules & Tips

Commas are confusing creatures. You don’t know when to use them and when to ditch them. Nevertheless, you must learn when to add a comma to your sentence if you want to make your writing

linguaholic.com

Commas after 'Regardless', 'Regardless of', and 'Anyway'

Commas after "regardless", "regardless of", and "anyway". #English #punctuation #comma #regardless

www.pristineword.com

 

[Tarheel]

When do I need to use a comma and when do I not need to use a comma?